JP3267735B2 - Biaxially stretched multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched multilayer film, and more particularly, to transparency and low-temperature heat sealability having high-speed automatic packaging suitability and significantly reduced contamination to packaging machines. The present invention relates to a biaxially stretched multi-layer film having a good quality.

[0002]

2. Description of the Related Art A biaxially stretched multilayer film, for example, a biaxially stretched polypropylene film having a heat-sealing layer laminated thereon, has various properties such as transparency and rigidity, and is used for food, tobacco,
It is widely used as a film for overlapping packaging such as a cassette tape, but with the recent development of a high-speed automatic packaging machine, the required quality of the film for automatic packaging suitability has been more advanced than ever. That is, the most important required performance in the film for overlap packaging is low-temperature heat sealing property. As a method for imparting this low-temperature heat sealing property, when producing a biaxially oriented polypropylene film, it has a low-temperature heat sealing property. resin,
For example, a method of laminating a propylene / ethylene random copolymer resin or a propylene / ethylene / butene-1 random copolymer has been developed, and further, by adding a second component such as polybutene-1 to this layer, Low temperature heat sealability has been greatly improved. Also, as a measure for improving the suitability of the film packaging machine in response to the recent increase in the speed of automatic packaging machines, a method of adding inorganic fine particles such as silica or calcium carbonate to the above resin (Japanese Patent Publication No. Hei 4-30347). Or a method of adding organic fine particles such as a spherical silicone resin powder (Japanese Patent Laid-Open No. 62-233248).
And the like, and a great improvement effect has been obtained with respect to speeding up of an automatic packaging machine.

[0003]

However, using a biaxially stretched multilayer film in which a low-temperature heat-sealable resin to which inorganic or organic fine particles are added is laminated on the surface of a biaxially stretched polypropylene film, high-speed operation for a long period of time is achieved. It has been found that the automatic packaging has a disadvantage that the added fine particles fall off and the packaging machine is contaminated. Therefore, an object of the present invention is to provide a biaxially stretched multilayer film which has high-speed automatic packaging suitability, has no pollution to packaging machines, and has excellent low-temperature heat sealability.

[0004]

[Means for Solving the Problems]

[Summary of the Invention] The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, have found that inorganic and organic fine particles having a specific particle size are used in a specific amount, and that an acid-modified fine particle is used. The inventors have found that the above object can be achieved by using a polypropylene having a molecular weight, and have completed the present invention. That is, the biaxially stretched multilayer film of the present invention is a crystalline propylene polymer or at least one surface of a base material layer containing the same as a main component, the following component A,
It is characterized by laminating layers of a composition comprising component B and component C. Component A: 100 parts by weight of a propylene-based random copolymer Component B: 0.05 to 0.6 parts by weight of inorganic or organic fine particles having an average particle diameter of 0.5 to 5 μm Component C: Number average molecular weight of 800 to 20, 000 acid-modified polypropylene 0.5 to 10 parts by weight

[Specific description of the invention] [I] Biaxially stretched multilayer film The biaxially stretched multilayer film of the present invention is formed on at least one surface of a crystalline propylene polymer or a base material layer mainly composed of the same. And a surface layer formed from a composition comprising the following components A, B and C. (1) Base material layer (a) Crystalline propylene polymer (essential component) The crystalline propylene polymer used in the base layer of the biaxially stretched multilayer film of the present invention includes a propylene homopolymer, Alternatively, a majority of propylene and other α-olefin (ethylene, butene, hexene, 4-methylpentene, octene, etc.), unsaturated carboxylic acid or its derivative (acrylic acid, maleic anhydride, etc.), aromatic vinyl monomer It is a random, block or graft copolymer with a monomer (such as styrene). The isotactic index (II) of such a crystalline propylene-based polymer is as follows:
Preferably it is 40% or more, especially 60% or more, especially 80% or more. Therefore, it is most preferable to use a propylene homopolymer. It is preferable to use those having an I of 90% or more, especially 95% or more, particularly 98% or more, from the viewpoint of the stiffness of the film, the paper dropping property of the film feeding portion, and the suitability for high-speed automatic packaging. The melt flow rate (MFR) is 0.5 to 10 g /
10 minutes, especially 1 to 5 g / 10 minutes is preferred. These crystalline propylene-based polymers may be used alone or as a mixture of a plurality of types of polymers, or may be a resin containing a crystalline propylene-based polymer as a main component.

(B) Other compounding materials (optional components) In the base layer of the biaxially stretched multilayer film of the present invention, the above-mentioned crystalline propylene polymer is used as a main component, and other compounding materials are deteriorated in properties. It may be blended in an amount not to be caused, for example, in a range of 30% by weight or less. Examples of such blending materials include ethylene polymer, butene polymer, petroleum resin, terpene resin, styrene resin and the like. And other thermoplastic polymers such as the above hydrocarbon polymers (including their hydrogenated products). Further, to the crystalline propylene polymer of the substrate layer, of course, additives such as stabilizers such as antioxidants and weathering agents, processing aids, coloring agents, antistatic agents, lubricants, and antiblocking agents are used. May be included. Among these additives, those containing an antistatic agent are particularly preferable. Preferred examples of the antistatic agent include fatty acid esters of glycerin, alkylamines, ethylene oxide adducts of alkylamines, and fatty acid esters thereof. In the case of a film to which good antistatic performance has not been imparted, static electricity may accumulate during running of the film, resulting in poor paper dropping properties.

(2) Surface Layer The surface layer used in the biaxially stretched multilayer film of the present invention is laminated on one or both sides of a substrate layer formed from the above-mentioned crystalline propylene polymer. These surface layers are formed from a resin composition for a surface layer comprising the following components A, B and C.

(A) Resin composition for surface layer Constituent component (essential component) Component A: Propylene random copolymer The propylene random copolymer used as the component A is a propylene / ethylene random copolymer or a propylene / ethylene random copolymer. Non-crystalline, for example, isotactic index (II) such as propylene / ethylene / butene-1 random copolymer is less than 80%, especially less than 60%, especially 4
Less than 0% of a propylene-based random copolymer resin can be mentioned. Specifically, the propylene / ethylene random copolymer resin has an ethylene content of 2 to 10% by weight, preferably 3 to 8% by weight, particularly preferably 4 to 6% by weight.
% By weight. If the propylene / ethylene random copolymer resin has an ethylene content lower than the above range, the heat sealability tends to decrease. In addition, those having a high ethylene content tend to have a sticky film and a reduced scratching property. The propylene / ethylene / butene-1 random copolymer resin has an ethylene content of 0.3 to 6% by weight, preferably 0.5 to 5%.
% By weight, particularly preferably 1 to 4% by weight, and a butene-1 content of 2 to 30% by weight, preferably 3 to 2% by weight.
It is 5% by weight, particularly preferably 5 to 20% by weight. If the propylene / ethylene / butene-1 random copolymer resin has an ethylene content or butene-1 content less than the above range, the heat sealability tends to decrease, and the ethylene content or butene-1 content If the content is too large, the film tends to be sticky and the scratching property tends to decrease. The propylene / ethylene random copolymer resin generally has an MFR of 0.4 to 1
00 g / 10 min, preferably 0.5 to 50 g / 10 min,
More preferably 1 to 20 g / 10 min, particularly preferably 2 to 20 g / 10 min.
10 to 10 g / 10 min.

Component B: Inorganic or Organic Fine Particles The fine particles used as the above component B have an average particle size of 0.1 to 0.3.
Inorganic or organic fine particles of 5 to 5 μm, preferably 1 to 4 μm. As the inorganic fine particles, for example,
Silica, zeolite, talc, kaolin and the like can be mentioned. Among them, it is preferable to use silica. Further, the shape is preferably spherical because it is excellent in the effect of improving the suitability for packaging. Examples of the organic fine particles include non-melting type polysiloxane powder, polyamide powder, acrylic resin powder, and condensation type resin powder having a triazine ring. It is preferable to use siloxane powder and crosslinked polymethyl methacrylate powder. Also,
It is preferable to use a spherical shape similarly to the inorganic fine particles. Inorganic or organic fine particles having an average particle size less than the above range cannot improve packaging suitability. Further, in the case of inorganic or organic fine particles having an average particle diameter exceeding the above range, even if the component C described below is added, it is not possible to improve the transparency and the removal of the fine particles.

Component C: Acid-Modified Polypropylene The acid-modified polypropylene used as the component C is as follows:
Number average molecular weight 800 to 20,000, preferably 1,0
00-18,000 acid-modified polypropylene (hereinafter sometimes abbreviated simply as “acid-modified low molecular weight PP”). The acid-modified low molecular weight PP is obtained by chemically adding an unsaturated carboxylic acid and / or an anhydride thereof described below to a low molecular weight polypropylene having a terminal double bond,
Alternatively, it is synthesized by reducing the molecular weight of ordinary acid-modified polypropylene, and at least a part thereof is acid-modified at its terminal. The acid-modified polypropylene obtained by the acid modification generally has a softening point of 1
It shows a temperature of 30 to 170 ° C., preferably 140 to 160 ° C., and generally has an acid value of 3 to 80 mg KO.
H / g, preferably 10 to 60 mgKOH / g.

The preferred low molecular weight polypropylene having a terminal double bond includes 1 to 1 per 1,000 carbon atoms.
It has 0, preferably 2 to 7 terminal double bonds, and has a number average molecular weight of 800 to 20,000, preferably 1,000 to
18,000. If the terminal double bond is less than the above range, desired acid modification may not be performed. If the terminal double bond exceeds the above range, the heat resistance of the acid-modified low molecular weight PP tends to decrease. . If the number average molecular weight is less than the above range, falling off of the fine particles cannot be prevented. On the other hand, when the number average molecular weight exceeds the above range, the heat sealing property and the prevention of falling off of the fine particles tend to decrease.

The acid modification is carried out by a melt grafting method or a solution grafting method.
At a reaction temperature of usually 100 to 270 ° C, preferably 130 to 240 ° C, usually for 0.5 to 30 hours, preferably 1 to 2 hours
The reaction is performed under the condition of a reaction time of 0 hour. In the solution grafting method, after completely dissolved in xylene, a peroxide is used in combination, and the reaction with an unsaturated carboxylic acid and / or an anhydride thereof is usually performed at 120 to 180 ° C., preferably 14 ° C.
The reaction is carried out at a reaction temperature of 0 to 160 ° C, usually for a reaction time of 1 to 20 hours, preferably 3 to 15 hours. Then, a precipitate is obtained using a large amount of acetone or the like. The product obtained by the acid modification contains generally 0.01 to 20%, preferably 0.05 to 15%, particularly preferably 0.1 to 10% by weight of unsaturated carboxylic acid and / or anhydride thereof.
Is desirably contained at a ratio of As long as it is contained in such a ratio, a directly acid-modified product may be diluted with an unmodified product. Such an acid-modified low molecular weight PP can be appropriately selected from commercially available products and used.

Unsaturated carboxylic acids The unsaturated carboxylic acids include (meth) acrylic acid,
Maleic acid, fumaric acid, itaconic acid and the like can be mentioned. Unsaturated carboxylic anhydride Examples of the unsaturated carboxylic anhydride include maleic anhydride, itaconic anhydride and citraconic anhydride, allyl succinic anhydride and nadic anhydride.
Among these, it is preferable to use maleic anhydride.

Other Constituents (Additional Components) In addition to these essential constituents, the surface layer of the biaxially stretched multilayer film of the present invention may further comprise: Additional components other than the above essential components can be added for other purposes. As the additional component, for example, the low-temperature heat sealability can be further improved by adding 5 to 45 parts by weight of a crystalline butene-1 polymer to 100 parts by weight of the above component A. Examples of such a crystalline butene-1 polymer include a homopolymer of butene-1 and a copolymer of butene-1 with another α-olefin such as ethylene and propylene. The MFR of these copolymers is 180 to 300 ° C
It is preferable to use one having a value equal to or larger than the MFR of the above-mentioned component A at the same temperature in the range of from the viewpoint that the transparency can be improved. Also,
In order to improve the suitability for high-speed packaging, it is preferable to add an organic lubricant such as various silicone oils and silicone gums. As a particularly preferred lubricant, 0.1 to 1 part by weight of a polydiorganosiloxane gum having a polymerization degree n of 3,500 to 8,000, or a viscosity of 100 to 100,
000 centistokes of silicone oil.

Blending Ratio The blending ratio of each component of the surface layer composition composed of the components A, B and C is determined based on a propylene random copolymer. Component B: Inorganic or organic fine particles The compounding amount of the inorganic or organic fine particles to be compounded as the component B in the propylene random copolymer is 0.05 with respect to 100 parts by weight of the propylene random copolymer. ~
0.6 parts by weight, preferably 0.1 to 0.5 parts by weight. If the amount is less than the above range, packaging suitability cannot be imparted. If the compounding amount exceeds the above range, falling of the fine particles cannot be prevented even if the component C is compounded, and also the transparency of the film deteriorates. Component C: Acid-Modified Low-Molecular-Weight PP The compounding amount of the acid-modified low-molecular-weight PP blended as the component C in the propylene-based random copolymer is 0.5 to 10 with respect to 100 parts by weight of the propylene-based random copolymer. Parts by weight, preferably 2 to 7 parts by weight. If the amount is less than the above range, falling off of the fine particles cannot be prevented. On the other hand, if the compounding amount exceeds the above range, not only is the heat sealing property deteriorated, but also the cost is increased, which is not preferable. Further, among the above-mentioned components B, by adding the above-mentioned component C to spherical fine particles having a great effect of improving the suitability for packaging, the effect of preventing the fine particles from falling off can be further exhibited.

Production of Composition for Surface Layer The composition for the surface layer constituting the surface layer of the biaxially stretched multilayer film of the present invention is obtained by mixing the above components A, B and C with a Henschel mixer, a V blender and a ribbon blender. And then kneading with a kneading machine such as an extruder. In addition, there is no problem if a master batch is prepared by blending the component B and the component C in a larger amount than a predetermined amount, and the master batch is diluted and used at the time of molding. However, it is desirable to avoid using a method in which the component B and the component C are separately blended and diluted at the time of molding, since the improvement effect is reduced.

(3) Thickness The thickness of the biaxially stretched multilayer film thus obtained is determined according to its use.
m, preferably in the range of 10 to 60 μm. The ratio of the surface layer to the intermediate layer is usually 1 to 20%, preferably 1.5 to 10%. In addition, the thickness of the surface layer in the thickness of such a biaxially stretched multilayer film is generally 0.2 to 3 μm, preferably 0.3 to 1.5 μm, and particularly preferably 0.5 to 1 μm. . If the thickness of the surface layer exceeds the above range, the suitability for packaging may be poor. When the thickness is less than the above range, uniform heat sealing strength may not be provided.

[II] Production of Biaxially Stretched Multilayer Film (1) Lamination The biaxially stretched multilayer film of the present invention is formed on at least one surface of a crystalline propylene-based polymer or a base material layer containing the same as a main component. And a multilayer film which can be produced by laminating and stretching a surface layer formed from the composition for a surface layer comprising the above-mentioned components A, B and C. As a method of laminating the surface layer composition comprising the components A, B and C on the biaxially stretched base material layer of the crystalline propylene polymer, for example, A method in which the composition for a surface layer is formed into a sheet by melt-coextrusion on one or both surfaces of the coalesced sheet and then biaxially stretched is preferred because this composition can be easily, uniformly and thinly laminated. However, a method in which the composition for a surface layer is melt-extruded and coated on an unstretched or uniaxially stretched base layer sheet and then biaxially stretched or uniaxially stretched in a direction perpendicular to the stretching direction of the base layer can also be adopted. .

(2) Elongation First of the above-mentioned biaxial stretching, longitudinal stretching can be performed by utilizing a difference in roll peripheral speed. That is, 90-
140 ° C., preferably 3 to 8 at a temperature of 105 to 135 ° C.
, Preferably 4 to 6 times, and subsequently in a transverse direction in a tenter oven 3 to 12 times, preferably 6 times.
Stretch up to 11 times. In order to prevent heat shrinkage at the time of heat sealing, it is desirable to heat set at a temperature of 120 to 170 ° C. subsequent to the transverse stretching.

(3) Other treatments Further treatments such as corona treatment can be performed for the purpose of promoting printability and bleeding of the antistatic agent.

[III] Applications The biaxially stretched multilayer film of the present invention has high suitability for high-speed automatic packaging, has significantly reduced contamination to packaging machines, and has high transparency and low-temperature heat sealability. Because of its good properties, it is suitable for high-speed automatic packaging, and is widely used as a film for overlapping packaging of foods, cigarettes, cassette tapes and the like.

[0022]

【Example】

[I] Evaluation method (1) 230 ° C., 2.16 in accordance with MFR ASTM-D-1238
It measured using the load of kg. (2) Haze Measured according to ASTM-D-1003. (3) Suitability for packaging Cigarettes were packed at a speed of 300 pieces / min using a packaging machine manufactured by Tokyo Automatic Machinery Co., Ltd., and the following evaluations were made. (i) Heat sealability After the packaging was completed, the degree of adhesion of the tobacco bottom-sealing seal was evaluated. (ii) Contamination of Packaging Machine The film was set on a packaging machine to a length of 2,000 m, and the degree of the amount of the inorganic or organic fine particles adhering to the packaging machine was visually evaluated according to the following criteria. ：: No powder was generated. ：: Powder generation is observed. X: Very much powder is generated.

[II] Experimental Examples Example 1 As a substrate layer, the MFR was 1.9 g / 10 min. I is 9
A mixture comprising 90 parts by weight of 8% crystalline polypropylene homopolymer powder, 10 parts by weight of a hydrogenated terpene resin, and 0.9 parts by weight of a fatty acid ester of polyoxyethylene alkylamine was used. On the other hand, in the surface layer, as the component A, an ethylene content of 2% by weight, a butene-1 content of 12% by weight,
90 parts by weight of a propylene / ethylene / butene-1 random copolymer resin having an MFR of 5.0 g / 10 min,
1. 10 parts by weight of an ethylene random copolymer resin are blended.
45 parts by weight, and a low molecular weight polypropylene having 4.2 terminal double bonds per 1,000 carbons as the component C was modified with maleic anhydride to obtain a number average molecular weight of 5,000.
0, a resin composition containing 3 parts by weight of a maleic anhydride-modified low molecular weight polypropylene having an acid value of 50 mgKOH / g and a silicone oil having a viscosity of 10,000 centistokes (hereinafter abbreviated as α-layer resin). ) Was used.
As the surface layer on the other side, only the propylene / ethylene / butene-1 random copolymer resin of the α layer resin (hereinafter abbreviated as β layer resin) was used. The crystalline polypropylene mixture of the base layer and the α-layer resin and the β-layer resin were each 115 mm in diameter, 20 mm in diameter, and 30 m in diameter.
Using a three-layer die from an m-diameter extruder, extrude into a three-layer laminated sheet having a thickness of α layer resin / base layer / β layer resin: 0.05 mm / 1 mm / 0.05 mm. Molded. This laminated sheet is stretched 5 times in the longitudinal direction at a temperature of 115 ° C. by continuously using the difference in roll peripheral speed.
A biaxially stretched multilayer film was produced by heat setting in a tenter oven at a temperature of 65 ° C. The thickness configuration of this film was 0.9 μm / 20 μm / 1.1 μm. After the corona discharge treatment was performed on the surface side of the β-layer resin of the obtained biaxially stretched multilayer film, cigarette packaging was performed so that the corona discharge treatment surface was inside. Table 1 shows the results.

Example 2 Component B used in the α-layer resin of Example 1 was prepared by adding an average particle diameter of 3 μm
Was changed to 0.3 parts by weight of a true spherical polysiloxane powder, and the number average molecular weight of Component C was modified from maleic anhydride to a low molecular weight polypropylene having 1.5 terminal double bonds per 1,000 carbon atoms. 000, acid value 30mgK
The same operation as in Example 1 was carried out except that 5 parts by weight of an OH / g maleic anhydride-modified low molecular weight polypropylene was used. Table 1 shows the results.

Example 3 Component B used in the α-layer resin of Example 2 was prepared by adding an average particle size of 4 μm.
Was carried out in the same manner as in Example 2 except that the powder was changed to 0.2 parts by weight of the true spherical crosslinked polymethyl methacrylate powder. Table 1 shows the results.

Comparative Example 1 The procedure of Example 2 was repeated except that the component C used in the α-layer resin of Example 2 was not added. Table 1 shows the results.

Comparative Example 2 Component C used in the α-layer resin of Example 2 was mixed with MFR 0.8
Modified by using benzoyl peroxide and maleic anhydride in polypropylene / 10 min. Performed as in Example 2. Table 1 shows the results.

[0028]

[Table 1]

[0029]

The biaxially stretched multilayer film of the present invention contains inorganic and organic fine particles having a specific particle size in a specific amount,
Also, by laminating a surface layer containing acid-modified low molecular weight polypropylene, it has good transparency and low-temperature heat-sealing properties, is suitable for high-speed automatic packaging, and can be used for long-term high-speed automatic packaging. It is industrially extremely useful because it can provide a biaxially stretched film without falling off and contaminating the packaging machine.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (4)

(57) [Claims] 1. A layer comprising a composition comprising the following components A, B and C on at least one surface of a crystalline propylene-based polymer or a base material layer comprising the same as a main component. Axial stretched multilayer film. Component A: 100 parts by weight of a propylene-based random copolymer Component B: 0.05 to 0.6 parts by weight of inorganic or organic fine particles having an average particle diameter of 0.5 to 5 μm Component C: Number average molecular weight of 800 to 20, 000 acid-modified polypropylene 0.5 to 10 parts by weight 2. The biaxially stretched multilayer film according to claim 1, wherein the propylene random copolymer is a propylene / ethylene random copolymer or a propylene / ethylene / butene-1 random copolymer. 3. The biaxially stretched multilayer film according to claim 1, wherein the inorganic or organic fine particles are silica, non-melting type polysiloxane powder, or crosslinked polymethyl methacrylate powder. 4. The biaxially stretched multilayer film according to claim 1, wherein the acid-modified polypropylene is at least partially or terminally acid-modified.